Side member of motor vehicle

ABSTRACT

A side member of a motor vehicle in which at least one of four side walls forming a closed tetragon has disposed thereon a plurality of beads extending transverse to the longitudinal direction of said at least one side wall. The beads are shorter than the width of said at least one side wall and are spaced at a pitch of P to (a+b)×(1±0.1)/2, where b is the transverse length said at least one side wall and a is the transverse length of a side wall adjacent said at least one side wall.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a side member of a motor vehicle, and moreparticularly to improvements in a side member of a motor vehicle,wherein an impact energy of impact load in the axial direction appliedto the side member can be absorbed by an axial compressive deformation.

2. Description of the Prior Art

There are known side members of a motor vehicle, wherein beads arrangedin the longitudinal direction are provided, and, when an impact load inthe axial direction is applied, an axial compressive deformation iseffected to absorb energy of the impact load.

However, generally, these conventional side members have been improperin shape, length of beads or pitch in the axial direction thereof, sothat it is difficult to stably effect the axial compressive deformation.

For example, normally a side member forms a closed section of arectangular form. However, when the beads are formed, crossing theopposing corner portions in the vertical direction on one side surfaceof the side member, the bending strength of the side member is reducedconsiderably, such that when an impact load is applied to the sidemember in the axial direction, the side member is bent before the sidemember is axially compressively deformed over the scope of the totallength thereof. The reason for this disadvantage is that when a bendingmoment acts on a tetragonal closed-section member, the stress caused bythis bending moment is mainly borned by the corner portions of thetetragon. As a consequence, when the beads are formed at the cornerportions bearing a large part of the stress, the bending stress must beborne by the other portions, causing the bending strength of the sidemember to be lowered considerably.

Furthermore, when the pitch of the beads is improper, as shown in FIG.11 for example, a disadvantage is presented such that an end portion 3of an expansive deformation portion 2 of the side member 1, which hasinitiated an axial compressive deformation, irregularly extends in thedirection of the deformation, such that a stable axial compressivedeformation cannot be obtained.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a side member of amotor vehicle, wherein a high resistant force is applied to a bendingstress caused when an impact load in the axial direction is applied, sothat the side member is not easily bent.

Another object of the present invention is to provide a side member of amotor vehicle, wherein when an axial compressive deformation is effectedby an impact load in the axial direction, portions to become troughs andportions to become ridges on the side wall are specified to effectstable axial compressive deformation.

To achieve the above-described objects, the present inventioncontemplates that, in a side member of a motor vehicle forming at leasttwo side walls of a tetragonal closed section and disposed substantiallyhorizontally in the longitudinal direction of a vehicle body in thevertical section of the vehicle body, at least on one side wall of thetwo adjacent side walls out of the four side walls, forming the closedsection, a plurality of beads, each of which is shorter than the lengthof the one side wall in a direction perpendicularly intersecting theaxis of the side member and not reaching the opposing corner portions ofthe one side wall, are arranged at a pitch of P=(a+b)×(1±0.1)/2, where ais the length of the one side wall of the tetragon and b is the lengthof the other side wall.

To the above end, the present invention contemplates that the beadscomprise a first group of beads concaved inwardly into the closedsection and a second group of beads convexed outwardly from the closedsection with a pitch half shifted from the first group of beads.

To the above end, the present invention contemplates that some beadsconvexed inwardly are suitably removed and corner beads are formed atcorner portions of opposite side portions of the bead-lacking positions.

To the above end, the present invention contemplates that corner beadsare formed at intermediate positions between the beads convexedoutwardly from the above-described beads and at positions where thebeads convexed outwardly are lacking.

To the above end, the present invention contemplates that when across-section of a member including the side member and forming theclosed section is symmetrical with respect to the vertical center linethereof, the beads are formed on the opposing vertical side walls of thetetragon at the same pitch in the axial direction of the side member andat the same phase.

To the above end, the present invention contemplates that when thecross-section of the member including the side member and forming theclosed section is not substantially symmetrical with respect to thevertical center line thereof, the beads are formed on the opposingvertical side walls of the tetragon at the same pitch and at a phaseshift of 1/2.

According to the present invention, the length of the beads is formed soas not to reach the corner portions of the side walls where the beadsare formed. Therefore, when a load acts on the side member in the axialdirection, the corner portions bear the bending stress, so that thebending strength is increased to obtain a stable axial compressivedeformation.

The pitch of the beads in the axial direction of the side member isspecified by the height and the width of the tetragon of the closedsection of the side member. When a load in the axial direction isapplied, the deformation of the side member is specified in the portionswhich become troughs and ridges, depending on the respective beads, sothat stable axial compressive deformation can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing one embodiment of the side memberof a motor vehicle according to the present invention;

FIG. 2 is an enlarged sectional view taken along the line II--II in FIG.1;

FIG. 3 is a perspective view showing the state where the side member isdeformed when an impact load in the axial direction of the side memberis applied thereto;

FIG. 4 is a perspective view showing a second embodiment of the presentinvention;

FIG. 5 is an enlarged sectional view taken along the line V--V in FIG.4;

FIG. 6 is a perspective view showing a third embodiment of the presentinvention;

FIGS. 7 and 8 are enlarged sectional views taken along the linesVII--VII and VIII--VIII in FIG. 6;

FIG. 9 is a perspective view showing a fourth embodiment of the presentinvention;

FIG. 10 is an enlarged sectional view taken along the line X--X in FIG.9;

FIG. 11 is a perspective view showing the state where the initial axialcompressive deformation is caused to the conventional side member of amotor vehicle;

FIG. 12 is a chart showing the relationship between the bending stressapplied to the side member and the sectional shape of the side member;and

FIGS. 13 to 15 are sectional views showing modifications of the sidemembers, to which is applied the present invention, and the sectionalshapes in the connected states between the side members and the panels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will hereunder be given of the embodiments of the presentinvention with reference to the drawings.

As shown in FIGS. 1 and 2, the first embodiment of the present inventionis such that, in a rectangular closed section 14 having a width a and aheight b and formed by a side member 10 and a panel 12 blocking anopening of the side member 10 and welded to upper and lower flanges 10Aand 10B and formed of, for example, a fender panel, a plurality of beads16, each of which has a length shorter than the length of the verticalside wall 10C in the vertical direction and each of which do not reachcorner portions in the vertical direction on the vertical side wall 10C,are arranged on the vertical side wall 10C opposed to the panel 12 at apredetermined pitch P in the axial direction of the side member 10.

The pitch P of the beads 16 in the axial direction of the side member 10is determined by the following equation, in accordance with the width aand the height b of the closed section 14:

    P=(a+b)×(1±0.1)/2                                 (1)

If the length of the beads 16 is shorter than the vertical side wall 10Cand does not reach the upper and the lower corner portions 10D and 10Eas described above, then the bending stress, caused when an impact loadin the axial direction of the the side member 10 acts on the side member10, mainly borne by the corner portions 10D and 10E, so that the bendingrigidity is increased, the side member 10 is not easily bent and astable axial compressive deformation is generated to the load in theaxial direction.

Furthermore, according to the above-described equation (1), it has beendetermined by the experiments conducted by the inventors of the presentinvention that, when a load in the axial direction is applied to theside member 10, a bulged-out portion of the side member 10 caused by theaxial compressive deformation does not extend irregularly, the pitch ofthe beads is not increased, the portions expanded outward by and theportions recessed into the side member 10, i.e. positions of ridge linesX and trough lines Y are regulated and the portions becoming the troughsand the ridges can be most suitably specified (Refer to FIG. 3).

Specifically, when the axial load acts on the side member 1 having thecross-section shown in FIG. 11, the bending stress thus caused is shownby a solid line S in FIG. 12. As shown in FIG. 12, when the bead 4 isformed so as to cover the total scope of the side wall 1 and reachingthe corner portions at the opposite sides, the stress borne by the wallbetween points A and B as shown in FIG. 12 becomes extremely low.

On the other hand, as shown in FIGS. 1 and 2, when the beads 16 areformed so as not to reach the corner portions 10D and 10E of thevertical side wall 10C as in the above embodiment, the bending stresscan be borne by the portion of the wall between two points B and C asshown in FIG. 12. As a result, the bending rigidity is increasedrelative to the case in which the beads 4 are provided as in FIG. 1.

Description will hereunder be given of the second embodiment of thepresent invention as shown in FIGS. 4 and 5.

In this second embodiment, beads 26 convexed outwardly are formed on aside member 20 having a shape similar to the side member of the firstembodiment.

The other aspect of this embodiment is identical to the ones in thefirst embodiment, so that the same reference numerals are used and thedescription will not be repeated.

The major difference between the second embodiment and the firstembodiment is that, in the first embodiment, when the axial load isapplied to the side member 10, the side wall 10C having the beads in theside member 10 is inwardly deformed at the positions of the beads 16. Inthe second embodiment, however, when the axial load is applied to theside member 20, the side wall 20C having the beads in the side member 20is outwardly deformed at the positions of the beads 26.

A description will hereunder be given of the third embodiment of thepresent invention shown in FIGS. 6 to 8.

In this third embodiment, the beads 16, concaved inwardly, and the beads26, convexed outwardly, are alternately formed on a side member 30having a shape similar to the one in the first embodiment at a pitch ofP/2. As in the first embodiment, the beads 26 convexed outwardly areformed at the positions where beads are bulged outwardly in the firstembodiment when the axial compressive deformation is caused.

As a result, the portions to become troughs and ridges in the sidemember 30 can be regulated and specified more reliably at the time ofthe axial compressive deformation.

Additionally, the beads 16 and 26 are formed only on the vertical sidewall of the side members 10, 20 and 30 each having a laterally directedhut type section, which is opposed to the panel 12. However, the presentinvention need not necessarily be limited to this, and, for example,there may be adopted to a closed section as shown in FIG. 10, a closedsection formed by an angle-shaped side member 50 and an angle-shapedpanel 32 as shown in FIG. 13, a closed section wherein a laterallydirected U-shaped side member 60 and a laterally directed U-shaped panel42 overlap at the center position in the widthwise direction as shown inFIG. 14, or a side member 70 singly forming a tetragonal closed sectionwithout being connected to a panel or the like as shown in FIG. 15.

The beads may be formed on at least on one side wall out of two opposingside walls. As a result, as in the fourth embodiment shown in FIGS. 9and 10, beads 36 may be formed on both a side member 40 and a panel 22connected thereto.

When the beads are formed on the two opposing side walls forming theclosed section 14, if the section of the side member or a connected bodyof the side member and the panel is not symmetrical with respect to thevertical center line thereof as shown in FIGS. 2, 10 and 13, then thebeads formed on the two opposing side walls are formed at the same pitchin the axial direction of the side member and at a phase shift of 1/2.

Furthermore, when the section is symmetrical with respect to thevertical center line thereof as shown in FIGS. 14 and 15, the beads areformed at the same pitch in the axial direction of the side member atthe same phase.

Additionally, as shown in FIGS. 9 and 10 for example, some of the beadson the side member 40 are removed, and instead, corner beads 40A, 40Bmay be formed at positions of an upper and a lower corner positions.

Here, since the corner beads 40A are concaved outwardly, when the beadsformed on the side member are convexed, the corner beads 40A are formedat intermediate positions, i.e. at a phase shift of 1/2.

What is claimed is:
 1. A side member of a motor vehicle, said sidemember being disposed substantially horizontally in the longitudinaldirection of a vehicle body, comprising:first, second, third and fourthside walls defining a tetragonal closed section in a vertical section ofthe vehicle body; a plurality of beads on at least one of said sidewalls, each of said beads extending in a transverse direction to saidlongitudinal direction and being shorter than the width of said at leastone side wall in said transverse direction and not extending to cornersdefined by said at least one side wall and side walls adjacent to saidat least one side wall, said beads being spaced at a pitch ofP=(a+b)×(1±0.1)/2 where b is the transverse length of said at least oneside wall and a is the transverse length of said adjacent side walls. 2.A side member of a motor vehicle as set forth in claim 1, wherein saidbeads comprise a first group of beads concaved inwardly into the closedsection and a second group of beads convexed outwardly from the closedsection with a pitch half shifted from the first group of beads.
 3. Aside member of a motor vehicle as set forth in claim 1, wherein cornerbeads are formed at positions where said beads convexed outwardly arelacking.
 4. A side member of a motor vehicle as set forth in claim 2,wherein corner beads are formed at positions where said beads convexedoutwardly are lacking.
 5. A side member of a motor vehicle as set forthin claim 1, wherein corner beads are formed at intermediate positionsbetween said beads convexed outwardly at positions where said beadsconvexed outwardly are lacking.
 6. A side member of a motor vehicle asset forth in claim 2, wherein corner beads are formed at intermediatepositions between said beads convexed outwardly at positions where saidbeads convexed outwardly are lacking.
 7. A side member of a motorvehicle as set forth in claim 1, wherein, when a cross-section of amember including said side member and forming said closed section issymmetrical with respect to a vertical center line thereof, said beadsare formed on opposing vertical walls of said tetragonal closed sectionat the same pitch in the axial direction of the side member and at thesame phase.
 8. A side member of a motor vehicle as set forth in claim 2,wherein, when a cross-section of a member including said side member andforming said closed section is symmetrical with respect to a verticalcenter line thereof, said beads are formed on opposing vertical walls ofsaid tetragonal closed section at the same pitch in the axial directionof the side member and at the same phase.
 9. A side member of a motorvehicle as set forth in claim 3, wherein, when a cross-section of amember including said side member and forming said closed section issymmetrical with respect to a vertical center line thereof, said beadsare formed on opposing vertical walls of said tetragonal closed sectionat the same pitch in the axial direction of the side member and at thesame phase.
 10. A side member of a motor vehicle as set forth in claim4, wherein, when a cross-section of a member including said side memberand forming said closed section is symmetrical with respect to avertical center line thereof, said beads are formed on opposing verticalwalls of said tetragonal closed section at the same pitch in the axialdirection of the side member and at the same phase.
 11. A side member ofa motor vehicle as set forth in claim 5, wherein, when a cross-sectionof a member including said side member and forming said closed sectionis symmetrical with respect to a vertical center line thereof, saidbeads are formed on opposing vertical walls of said tetragonal closedsection at the same pitch in the axial direction of the side member andat the same phase.
 12. A side member of a motor vehicle as set forth inclaim 6, wherein, when a cross-section of a member including said sidemember and forming said closed section is symmetrical with respect to avertical center line thereof, said beads are formed on opposing verticalwalls of said tetragonal closed section at the same pitch in the axialdirection of the side member and at the same phase.
 13. A side member ofa motor vehicle as set forth in claim 1, wherein, when a cross-sectionalshape of said member including said side member and forming saidtetragonal closed section is not substantially symmetrical with respectto a vertical center line thereof, said beads are formed on opposingvertical side wall of said tetragonal closed section at the same pitchand at a phase of shift at 1/2.
 14. A side member of a motor vehicle asset forth in claim 2, wherein, when a cross-sectional shape of saidmember including said side member and forming said tetragonal closedsection is not substantially symmetrical with respect to a verticalcenter line thereof, said beads are formed on opposing vertical sidewall of said tetragonal closed section at the same pitch and at a phaseof shift at 1/2.
 15. A side member of a motor vehicle as set forth inclaim 3, wherein, when a cross-sectional shape of said member includingsaid side member and forming said tetragonal closed section is notsubstantially symmetrical with respect to a vertical center linethereof, said beads are formed on opposing vertical side wall of saidtetragonal closed section at the same pitch and at a phase of shift at1/2.
 16. A side member of a motor vehicle as set forth in claim 4,wherein, when a cross-sectional shape of said member including said sidemember and forming said tetragonal closed section is not substantiallysymmetrical with respect to a vertical center line thereof, said beadsare formed on opposing vertical side wall of said tetragonal closedsection at the same pitch and at a phase of shift at 1/2.
 17. A sidemember of a motor vehicle as set forth in claim 5, wherein, when across-sectional shape of said member including said side member andforming said tetragonal closed section is not substantially symmetricalwith respect to a vertical center line thereof, said beads are formed onopposing vertical side wall of said tetragonal closed section at thesame pitch and at a phase of shift at 1/2.
 18. A side member of a motorvehicle as set forth in claim 6, wherein, when a cross-sectional shapeof said member including said side member and forming said tetragonalclosed section is not substantially symmetrical with respect to avertical center line thereof, said beads are formed on opposing verticalside wall of said tetragonal closed section at the same pitch and at aphase of shift at 1/2.